1. Field of the Invention
The present invention relates to an improved and novel link mechanism in a pushbutton-operated waveband or station selector or tuner.
2. Description of the Prior Art
In the pushbutton-operated waveband or station selector, as a selected pushbutton is depressed, the memory plate is moved and coupled with the core slide so that the pressure applied to the pushbutton is transmitted to the core slide on which a core is fitted, this core being thus inserted into or extracted out of the tuning coil, or as the manual tuning knob is turned, it causes the core slide to move so as to change the inserted position of the core inside the tuning coil. In many of such conventional techniques, the core slide on which the coil is secured moves in a direction different from that in which the memory plate to shift the core slide or the tuning shaft-side shifting member moves. For example, the memory plate and the tuning knob-side shifting member are so disposed as to be movable in the direction of the pusbutton width, while the core slide is so disposed as to be movable in the direction perpendicular (front-rear direction of the pushbutton) to the moving direction of the memory plate and tuning knob-side shifting member. Therefore, in order to operatively couple these members, there is provided between them a link which provides for an operative coupling of them and changes the moving directions of them.
In the conventional pushbutton-operated waveband or station selector, the arms of a link are disposed perpendicular to the moving directions of the members connected with the link arms as shown in FIG. 1. As seen in FIG. 1, a link 91 having generally an L shape is rotatably fitted at the corner portion thereof on a pivotal shaft 92; one of the arms 91A of this link 91 has provided at the end thereof a guide roller 93 which is inserted into an elongated guide hole 95 formed in a memory plate 94 at the end thereof and which forms a right angle with the moving direction of the memory plate. The other arm 91B of the link 91 is extended to a core slide 96 which moves in a direction perpendicular to the memory plate 94; a guide roller 97 provided at the end of this second arm 91B is inserted into a guide hole 98 formed in the core slide 96 and which forms a right angle with the core slide.
In such conventional type of pushbutton-operated waveband or station selector, when the memory plate 94 is moved laterally by depressing the pushbutton, the first arm 91A coupled by means of the guide roller 93 and guide hole 96 to the memory plate is pressed so that the link 91 pivots about its pivotal shaft 92. Then, the core slide 96 coupled to the end of the second arm 91B of the link 91 by means of the guide roller 97 and guide hole 98 is moved so that a core 99 fitted on the core slide 96 is moved for selection of a waveband or station.
In the above-mentioned conventional pushbutton-operated waveband or station selector, the guide rollers 93 and 97 provided at the ends of link arms delineate a circular orbit about the pivotal shaft 92 so that they reciprocate in the guide hole 95 in the memory plate and guide hole 98 in the core slide in the direction of the guide hole length as shown in FIG. 2. Namely, the memory plate and core slide moves in the linear direction, while the guide rollers inserted in the guide holes formed in the memory plate and core slide, respectively, are reciprocated along the edges of the guide holes. For example, when the core slide 96 is positioned on this side, the second arm 91B of the link 91 forms with the moving direction of the core slide an angle smaller than right angle; the guide roller 97 is then positioned inside the guide hole 98 (on the side of pivotal shaft 92). As the memory plate 94 moves and so the link 91 starts pivoting, the end of the second arm 91B moves upward while the guide roller 97 moves outwardly within the guide hole 98. At this time, the core slide 96 in which the guide hole is formed will be forced outwardly. When the link 91 pivots and the second arm 91B and core slide move in such directions, respectively, as form together a right angle, the guide roller 97 reaches an outermost position of the guide hole 98, which position being a point of inflection around which the guide roller moves inwardly of the guide hole while forcing the core slide 96 upwardly. Accordingly, the core slide 96 is so forced that it is pressed inwardly (in a direction opposite to that in which it is pressed before the point of inflection is reached. As the result, while it is moved in front-rear direction, the core slide 96 is deflected in right-left direction by the link so that the core fitted on the core slide 96 wobbles, which is incovenient in that a frequency deviation occurs at selection of a waveband or station; further, if the core slide 96 is applied with a force which causes the core to wobble in right-left direction, the core slide 96 itself will not be smoothly moved in front-rear direction, which is also inconvenient in that a large force is required to operate the pushbutton in order to move the core slide 96. In addition, since the existence of such point of inflection causes the guide roller to rotate within the guide hole 97 in a different directions at points short of and beyond the point of inflection. Thus, a pushing force is not smoothly transmitted from the link to the core slide 96.
Such phenomenon does not occur only at the coupling between the link 91 and core slide 96, but also at the coupling between the first arm 91A and the memory plate 94 in the conventional apparatus shown in FIG. 1.
In the pushbutton-operated waveband or station selector or tuner, the member on the tuning shaft side is coupled with the core slide 96 by means of another link so that the core slide 96 may be moved in front-rear direction by operating the tuning shaft on the manual tuning side; if a point of inflection of the link exists in such coupling portion, the entire pushbutton-operated waveband or station selector incurs many factors which cause the loss of power transmission for movement of the core slide and make unstable the movement of core slide, which is a great drawback in improvement in performance of the pushbutton-operated waveband or station selector.